Conductive fluoropolymers

ABSTRACT

The invention provides a melt-processable conductive fluorothermoplastic composition comprising three components. The first component is at least one melt-processable, thermoplastic fluoropolymer component having its interpolymerized units derived from (i) at least 50 wt % of TFE, and (ii) one or more ethylenically-unsaturated monomers represented by the formulas (a) CF 2 ═CF—R f , (b) CF 2 ═CF—O—R f ′, and (c) CH 2 ═CR 2 , wherein R f  is a perfluoroalkyl of 1 to 8 carbon atoms, R f ′ is R f  or a perfluoroalkoxy of 1 to 8 carbon atoms, and R is selected from H, F, Cl, or an aliphatic group having from 1 to 8 carbon atoms which may have F or Cl substituents. The thermoplastic fluoropolymer component is substantially free of interpolymerized units derived from VDF. The second component is from about 0.1 to about 10 weight percent of a hydrocarbon polymer, and the third component is from about 1 to about 20 weight percent of conductive filler. The invention also provides a method for making fluorothermoplastic compositions and shaped articles comprising a conductive fluorothermoplastic composition.

This application is a div of Ser. No. 09/716,806, filed Nov. 20, 2000now U.S. Pat. No. 6,533,955.

TECHNICAL FIELD

This invention relates to electrically conductive, thermoplastic meltprocessable compositions that employ a major amount of afluorothermoplastic polymer, and minor amounts of an electricallyconductive material and a polyolefin.

BACKGROUND

Fluoropolymers are often used for their desirable properties, such aslow surface tension, high thermal stability, and high resistance tochemicals, oils, and/or solvents.

Examples of fluoropolymers include copolymers of tetrafluoroethylenewith one or more fluorinated monomers such as hexafluoropropylene orperfluoropropyl vinyl ether, and/or non-fluorinated monomers such asethylene or propylene.

Often it is desirable that the fluoropolymer have a lower electricalresistance or even be electrically conductive. Fluoropolymers aretypically made more electrically conductive by adding electricallyconductive fillers (e.g., carbon black, carbon fibers, etc.). However,the addition of such fillers has certain negative effects on theproperties of the fluoropolymers. For example, while adding conductivefillers desirably enhances the electrically conductivity of thefluoropolymer, it also often undesirably reduces the melt processabilityof the fluoropolymer.

DISCLOSURE OF INVENTION

The present invention provides a thermoplastic melt-processablefluoropolymer with lower electrical resistivity without increasing thelevel of the conductive filler. Hydrocarbon polymers, such aspolyolefins, are well known in the art as electrical insulators.Surprisingly, adding a normally insulating hydrocarbon polymer to whatwould be a conductive composition actually improves the conductivity ofthe resultant mixture in this invention. The present invention alsoprovides lower-resistivity fluoropolymers with improved processabilityand higher melt flow indices than known materials having comparableresistivity.

Briefly, the present invention provides a melt-processable conductivefluorothermoplastic composition comprising a blend of at least threecomponents. The first component provides a major amount (i.e., at least50 weight percent) of at least one melt-processable, thermoplasticfluoropolymer component. This first component has its interpolymerizedunits derived from (i) at least 50 weight percent (wt %) oftetrafluoroethylene (TFE), and (ii) one or moreethylenically-unsaturated monomers represented by the formulasCF₂═CF—R_(f), CF₂═CF—O—R_(f)′, and CH₂═CR₂. In the preceding formulas,R_(f) is a perfluoroalkyl of 1 to 8, preferably 1 to 3, carbon atoms,R_(f)′ is R_(f) or a perfluoroalkoxy of 1 to 8, preferably 1 to 3,carbon atoms, and R is selected from H, F, Cl, or an aliphatic grouphaving from 1 to 8, preferably 1 to 4, carbon atoms which aliphaticgroup may have F or Cl substituents. The first component has less than 5wt % of its interpolymerized units derived from vinylidene fluoride. Thesecond component is a hydrocarbon polymer, present in the blend at alevel from about 0.1 to about 10 wt %. The third component is aconductive filler, present in the blend at a level from about 1 to about20 wt %.

The present invention also provides a method of improving volumeresistivity of a melt-processable conductive fluorothermoplasticcomposition comprising the steps of providing at least the threecomponents described above, and mixing the components.

The present invention also provides shaped articles incorporating afluorothermoplastic composition as described above.

The extrudates of the present invention substantially retain propertiesof the fluoropolymer, such as thermal stability and/or chemicalresistance. These extrudates exhibit lower resistivity than knownfluorothermoplastic compositions having similar levels of conductivefillers. More specifically, the inventive compositions have a volumeresistivity below about 1×10⁴ ohm cm, more preferably below about 1×10²ohm cm.

The lower resistivity is surprisingly achieved while maintaining goodmelt processability or extrusion behavior. The melt flow indices of theinventive compositions do not decrease as rapidly as known materialswhen the level of conductive filler is increased. Thus, the extrudatesof the inventive blend composition can be extruded at higher outputrates and at much higher shear rates with much reduced shear stress, ascompared to known fluorothermoplastic compositions having similarresistivity levels. These inventive extrudates also have good surfacequalities, particularly smoothness, and are otherwise relatively free ofobjectionable surface melt defects.

DETAILED DESCRIPTION

The melt-processable conductive fluorothermoplastic composition of thepresent invention generally has a sufficient quantity of itsinterpolymerized units derived from TFE to provide a desirable level ofchemical resistance, while being a melt-processable thermoplasticfluoropolymer. That is, the final composition remains thermoplastic. Inthis thermoplastic fluoropolymer, the level of interpolymerized unitsderived from TFE generally ranges from about 50 wt % to about 98 wt %.

In one group of fluoropolymers useful in the present invention themelt-processable, thermoplastic fluoropolymer has interpolymerized unitsderived from TFE and one or more ethylenically-unsaturated monomers ofthe formula CF₂═CF—R_(f), wherein R_(f) is a perfluoroalkyl of 1 to 8,preferably 1 to 3, carbon atoms.

Typically, fluoropolymers of this group have a combination of 80 to 90wt % (preferably 84 to 88 wt %) of their units derived from TFE.Correspondingly, the balance of the fluoropolymer is one or moreethylenically-unsaturated monomers of the formula CF₂═CF—R_(f)(preferably hexafluoropropylene (HFP)), although it may further containup to about 2% of one or more ethylenically-unsaturated monomers of theformula CF₂═CF—O—R_(f)′ (preferably perfluoropropylvinylether). In thisdocument, perfluoropropylvinylether (PPVE) includes CF₂═CF—O—CF₂CF₂CF₃(also referred to as PPVE-1) and/or CF₂═CF—O—CF₂CF(CF₃)OCF₂CF₂CF₃ (alsoreferred to as PPVE-2).

In another group of fluoropolymers useful in the present invention, thethermoplastic fluoropolymer has interpolymerized units derived from TFEand one or more ethylenically-unsaturated monomers of the formulaCF₂═CF—O—R_(f)′. More specifically, fluoropolymers useful in the presentinvention have a combination of 85 to 98 wt % (preferably 90 to 97 wt %,more preferably 95 to 97 wt %) of their units derived from TFE. Thebalance of the fluoropolymer is from about 15 to about 2 wt %(preferably 10 to 3 wt %, more preferably 5 to 3 wt %) of one or moreethylenically-unsaturated monomers of the formula CF₂═CF—O—R_(f)′(preferably PPVE), although this fluoropolymer composition may furthercontain up to about 6 wt % of one or more ethylenically-unsaturatedmonomers of the formula CF₂═CF—R_(f) (preferably HFP).

Thus, fluoropolymers containing interpolymerized units derived from TFEand one, two, three, or more comonomer(s) are within the scope of thepresent invention.

Specific monomers of the formula CF₂═CF—R_(f)′ useful in the presentinvention include CF₂═CFCF₃ and CF₂═CFCF₂CF₃.

Specific monomers of the formula CF₂═CF—O—R_(f)′ useful in the presentinvention include CF₂═CF—O—CF₃, CF₂═CF—O—CF₂CF₃, CF₂═CF—O—CF₂CF₂CF₃(PPVE-1), CF₂═CF—O—CF₂CF₂CF₂OCF₃, CF₂═CF—O—CF₂CF(CF₃)OCF₂CF₂CF₃(PPVE-2), and CF₂═CF—O—CF₂CF(CF₃)OCF₂CF(CF₃)OCF₂CF₂CF₃.

Another group of monomers useful in combination with TFE includesethylenically-unsaturated monomers of the formula CH₂═CR₂. In thisformula R is selected from H, F, Cl, or an aliphatic group having from 1to 8, preferably 1 to 4, carbon atoms which may have F or Clsubstituents. This group of monomers includes hydrocarbon olefins suchas ethylene and propylene.

Fluoropolymers useful in the present invention also include combinationswherein the thermoplastic fluoropolymer has interpolymerized unitsderived from TFE, at least one ethylenically-unsaturated monomer of theformula CH₂═CR₂, and either one or more ethylenically-unsaturatedmonomer(s) of the formula CF₂═CF—R_(f), or one or moreethylenically-unsaturated monomer(s) of the formula CF₂═CF—O—R_(f)′, orboth. More specifically, this group of fluoropolymers further includescombinations wherein the thermoplastic fluoropolymer hasinterpolymerized units derived from TFE, an olefin such as ethylene orpropylene, one or more ethylenically-unsaturated monomers of the formulaCF₂═CF—R_(f) (preferably RFP), and one or more ethylenically-unsaturatedmonomers of the formula CF₂═CF—O—R_(f)′ (preferably PPVE). Suchfluoropolymers can have a combination of 60 to 80 wt % of their unitsderived from TFE and about 10 to about 25 wt % ethylene. In addition,the balance of the fluoropolymers in this group optionally includesmonomers selected from up to about 30 wt % of one or moreethylenically-unsaturated monomers of the formula CF₂═CF—R_(f)(preferably HFP), and optionally up to about 15 wt % of one or moreethylenically-unsaturated monomers of the formula CF₂═CF—O—R_(f)′(preferably PPVE).

At least one melt-processable, thermoplastic fluoropolymer is requiredin the present invention. Two or more such fluoropolymers of the same ordifferent compositions also can be used. For example, a first polymerhaving a low melt flow index may be used with a second polymer of thesame or similar composition but having higher melt flow index than thefirst polymer. In addition, a fluoropolymer derived from TFE and one ormore monomers having the formula CF₂═CF—R_(f) may be used with anotherfluoropolymer derived from TFE and one or more monomer(s) having theformula CF₂═CF—O—R_(f)′.

In preparing the blends of this invention, those fluoropolymerssubstantially free of interpolymerized units derived from vinylidenefluoride (VDF) are preferred. That is, the fluoropolymers contain lessthan 5 wt %, more preferably less than 2 wt %, and most preferably 0 wt% of interpolymerized units derived from VDF.

Commercial fluoropolymers which can be used include copolymers ofperflourinated ethylene-propylene (PEP) such as FEP 6307, FEP 6322;copolymers of tetrafluoroethylene and perfluoropropylvinyl ether (PFA)such as PFA 6502N; copolymers of ethylene and tetrafluoroethylene (ET orETFE) such as ET 6060, ET 6430, ET 6235J, ET 6235G copolymers ofhexafluoropropylene, tetrafluoroethylene, and ethylene (1-ITE) such asHTE 1500, and HTE 1700, all from Dyneon LLC (Oakdale, Minn.); Teflon®PFA fluoropolymer grades 340, 345, 350, 440HP, 450HP available fromDuPont (Wilmington, Del.); Teflon® FEP fluoropolymer grades 100, 140,160, CJ-95N available from DuPont; Teflon™ PFA fluoropolymer gradeAP238SG, AP211SH, Neoflon™ FEP, and Neoflon™ ETFE fluoropolymer gradesEP610 and EP620 available from Daikin Industries, Ltd. (Osaka, Japan);and copolymers of tetrafluoroethylene and perfluoromethylvinyl ether(MFA) available as Hyflon® MFA 620 and MFA 640 from Ausimont S.p.A.(Milan, Italy).

The hydrocarbon polymer in this invention comprises a non-fluorinatedpolymer whose backbone comprises carbon and hydrogen atoms. While heteroatoms such as nitrogen, oxygen, etc. may be present in limited amounts(e.g., less than about 5 wt %) the backbone preferably consists of onlycarbon and hydrogen. Examples of useful hydrocarbon polymers includepolyolefin, such as, for example, polyethylene and polypropylene,low-density polyethylene and high-density polyethylene, and blends oftwo or more of these. The preferred polyolefins are thermoplastichydrocarbon polymers that are homopolymers of ethylene and propylene andcopolymers of ethylene with 1-butene, 1-hexene, 1-octene,4-methyl-1-pentene, or propylene. Commercially available hydrocarbonpolymers which can be used in this invention include, for example,Escorenem™ LL-1001.09, LL-3001.00, LL-5252.09, LD411.09, and LD760.36polyethylenes, from Exxon Chem. Co.; ER1833 polyethylene from ChevronChemical Co.; Novapol™ TF 0119F polyethylene from Novacor ChemicalsInc.; Dowlex™ 2047 polyethylene from Dow Chemical Co.; Marlex™ HMN 4550polyethylene from Phillips 66 Co.; and 3374X polypropylene from Fina Oiland Chemical Co. Examples of other hydrocarbon polymers that may beuseful in the present invention include polystyrene, polyisoprene,polyisobutylene, polybutadiene, polyvinyl acetate, and polyvinylalcohol.

The hydrocarbon polymer and the fluoropolymer in the fluoropolymercompositions of the invention are immiscible. Generally, this can beshown by preparing a sample composition without the conductive filler(which typically imparts a color) and observing under an opticalmicroscope, or by observing the cloudy, white, or opaque appearance ofextrudates of the sample composition.

The particular blend components chosen can alter the particular amountof hydrocarbon polymer to be used, and simple sample extrusions can berun to determine that particular amount. The lower limit of amount ofthe hydrocarbon polymer to be blended with the fluoropolymer andconductive filler will generally be an amount at which a smallerdecrease in melt flow index occurs in the blend, as compared to a blendof the same fluoropolymer and conductive filler that is not blended withthe hydrocarbon polymer. Generally, the amount of the hydrocarbonpolymer will be about 0.1 to about 10 wt %, more preferably about 0.5 to4 wt % of the total blend including the fluoropolymer, the conductivefiller, and the hydrocarbon polymer.

The conductive filler used in preparing the conductive fluoropolymercompositions of this invention can be any of those known materials addedto resins to reduce resistivity or render the resin system moreconductive. One such filler is carbon black particulate. Generally, theconductive carbon black particles to be used will have high surfacearea, e.g., greater than 150 m²/g, high structure, e.g., dibutylphthalate absorption (DBT) numbers preferably greater than 150, and lowvolatility, e.g., volatile contents of less than 2.5 wt %. Conductivegrades of carbon black which can be used in this invention includesuper-conductive, extra-conductive, and P-type blacks with particlesizes ranging from 15 to 40 nm, nitrogen surface area of 40 to 1500m²/g, and densities of about 10 to 30 pounds per cubic feet (0.16 to0.48 g/cc). Commercial conductive carbon black particulates which can beused in this invention include, for example, Ketjen™ EC-300JD andEC-600JD, Vulcan™ XC-72, and Printex™ XE-2. Another such conductivefiller is graphite fibers.

The amount of conductive filler to be used in preparing thefluoropolymer compositions of this invention will be that amountsufficient to impart desired conductivity thereto and yet permit desiredmelt processing of the mixture. Generally, the conductive filler amountwill be 1 to about 20 wt % (preferably about 4 to about 11 wt %) of theconductive fluoropolymer composition, with lower quantities generallyproviding higher resistivity in the final fluoropolymer. For a givenlevel of conductive filler, the resistivity also depends upon the typeand level of the hydrocarbon polymer.

The blends of fluoropolymer, hydrocarbon polymer, and conductive fillercan be prepared by any suitable means. This includes, for example,blending means typically used in the plastics industry, such as usingseparate gravimetric feeders for each component to supply the selectedratio of components into a mixing unit. The mixing unit may in turn feedthe mixture into an extruder, such as a reciprocating single screwextruder, or the mixing unit may itself be an extruder, preferably atwin screw extruder A premix of at least two components (e.g., thehydrocarbon polymer and conductive filler) may also be prepared beforefeeding this premix to the extruder along with any other necessarycomponent(s) (e.g., the fluoropolymer). In addition, a melt blendedpremix of one or more fluoropolymers and the hydrocarbon polymer maythen be mixed with the conductive filler.

The ratio of components in the premix or other blend need not be withinthe final range desired. For example, a master batch of two componentsmay be let down with a third component to reach an intermediate targetcomposition or a final composition.

A uniform distribution of the components can provide lower resistivityat the same weight percent conductive filler than a less-uniformdistribution. Thus, the mixing extruder preferably uniformly distributesthe hydrocarbon polymer and conductive filler throughout thefluoropolymer. The mixing operation is conveniently carried out at atemperature above the melting point(s) of the polymers. Thefluoropolymer and the hydrocarbon polymers may be used in any desirableform, e.g., powders, pellets, and granules.

In preparing shaped articles, such as film, tubing, or heat tracingcable, of the conductive fluoropolymer blend compositions of thisinvention, various extruders or other melt shaping equipment known inthe art of polymer melt-processing can be used. Preferably the blendcomponents can be melt blended in a mixing extruder and the mixturemelt-processed therein, for example, at 200 to 400° C., depending uponthe melting point, melt viscosity, and thermal stability of the blend,to produce extrudates or shaped articles.

The melt blended mixture of fluoropolymer, conductive filler, andhydrocarbon polymer also can be pelletized or comminuted into a desiredparticulate size and then fed to a melt processor, which will typicallybe an extruder, to melt-process the blended mixture. Different types ofextruders which can be used to extrude the fluoropolymer compositions ofthis invention are described, for example, in “Polymer Extrusion” by C.Rauwendaal, Hansen Publishers, pages 23-48 (1986). The melt-processingequipment is preferably corrosion-protected.

The die design of the extruder can vary, depending on the extrudatedesired. For example, an annular die is useful to extrude tubing, suchas for fuel system hose or tubing such as that described in U.S. Pat.No. 5,284,184 (Noone et al.), the description of which is hereinincorporated by reference.

The benefits of the present invention are achieved by using a widevariety of thermoplastic fluoropolymers. Thus, while a specificfluoropolymer may perform somewhat differently than another specificfluoropolymer, it is not critical to the present invention whichthermoplastic fluoropolymer is used. It has been suggested that limitingthe number of certain types of end groups on the fluoropolymer providescertain benefits. It has been discovered that this limitation is notimportant in the present invention. For example, the level of unstableend groups can be above 100 ppm in the thermoplastic fluoropolymer ofthe present invention.

Objects and advantages of this invention are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention.

EXAMPLES

The following materials were used in the examples:

FEP X 6307 A thermoplastic fluoropolymer from Dyneon LLC, Oakdale, MNthat was derived from a copolymerization of TFE and HFP, and had atleast 100 unstable end groups per million carbon atoms. The meltingpoint was 250° C., and the melt flow index at 372° C. and 5 kg was 16g/10 min. Vulcan ™ XC-72 A carbon black from Cabot Corp., Houston, TX.Printex ™ XE-2 A carbon black from DeGussa-Hüls Corp., Ridgefield Park,NJ Ketjen ™ EC 600 JD A carbon black from Akzo Chem. Co., TheNetherlands. Escorene ™ LL-1001.09 A polyethylene from Exxon Chem. Co.,Houston, TX.

Testing:

The Melt Flow Index (MFI) (or Melt Flow Rate (MFR)) was measured usingthe method described by ASTM D1238 at 5 kg and 372° C. It is reported ingrams per 10 minutes. The specifications for FEP testing are given byASTM D2116.

Volume Resistivity was measured using the method described by ASTM D957,and reported in ohm cm.

Example 1

This example demonstrated high melt flow and low resistivity.

In Example 1, a blend of 89 wt % FEP X 6307, 9 wt % Vulcan™ XC-72, and 2wt % Escorene™ LL-1001.09 was fed into a 30-mm twin screw extruderoperating at 670 to about 700° F. (354 to 371° C.) and 88 rpm. Thefluorothermoplastic blend was extruded into sample bars for testing.

The extruded material was substantially free of melt defects.

Comparative Example 1 (CE 1)

A blend of 91 wt % FEP X 6307 and 9 wt % Vulcan™ XC-72 was mixed as inExample 1.

Example 1 showed much higher melt flow index and dramatically lowervolume resistivity than CE 1.

Example 2

This example also demonstrated the high melt flow and low resistivityadvantages of the present invention.

Example 2 was made as Example 1, except that a blend of 92.5 wt % FEP X6307, 5 wt % Printex™ XE-2, and 2.5 wt % Escorene™ LL-1001.09 was usedand the extruder was maintained at 82 rpm.

The extruded material was substantially free of melt defects.

Comparative Example 2

Comparative Example 2 (CE 2) was prepared as in Example 2, except that ablend of 95.5 wt % FEP X 6307 and 4.5 wt % Ketjen™ EC 600 JD was used.This carbon black is known in the art to provide somewhat moreconductivity at similar loading levels as the Printex™ XE-2. Thus, thiscomparative example would be expected to have similar properties as anotherwise similar material that has a slightly higher loading ofPrintex™ XE-2.

The inventive material of Example 2 had much higher melt flow index,lower volume resistivity, and similar mechanical properties, as comparedto CE2.

The following tables include compositions of each material and testresults.

TABLE 1 Compositions Example No.: 1 CE1 2 CE2 FEP X 6307 89 91 92.5 95.5Vulcan ™ XC-72 9 9 Printex ™ XE-2 5 Ketjen ™ EC 600 JD 4.5 Escorene ™LL-1001.09 2 2.5

TABLE 2 Test Results Example No. 1 CE1 2 CE2 Melt Flow Index 7.98 1.974.91 0.24 (g/10 min; 372° C., 5 kg) Volume Resistivity 2.3 × 10¹ 1.03 ×10⁸ 5.6 × 10¹ 2.4 × 10² (ohm cm)

These examples demonstrated the advantages of the present invention.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand principles of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth hereinabove. All publications and patents are hereinincorporated by reference to the same extent as if each individualpublication or patent was specifically and individually indicated to beincorporated by reference.

What is claimed is:
 1. A melt-processable conductive fluorothermoplasticcomposition comprising: A) a major amount of at least onemelt-processable, thermoplastic fluoropolymer having itsinterpolymerized units derived from (i) at least 50 weight percent (wt%) of tetrafluoroethylene (TEE), (ii) one or moreethylenically-unsaturated monomers represented by the formula (a)CF2═CF—O—R_(f)′, and, optionally, one or more ethylenically-unsaturatedmonomers represented by the formula (b) CH2═CR2 wherein Rf′ is aperfluoroalkyl of 1 to 8 carbon atoms or a perfluoroalkoxy of 1 to 8carbon atoms, and R is selected from H, F, Cl, or an aliphatic grouphaving from 1 to 8 carbon atoms which may have F or Cl substituents,provided that the thermoplastic fluoropolymer or has less than 5 wt % ofits interpolymerized units derived from vinylidene fluoride (VDF); B)from about 0.1 to about 10 weight percent of a hydrocarbon polymer; andC) from about 1 to about 20 weight percent of conductive filler.
 2. Thecomposition of claim 1 wherein thermoplastic fluoropolymer has less thanabout 2 wt % of its interpolymerized units derived VDF.
 3. Thecomposition of claim 1 wherein th thermoplastic fluoropolymer hasinterpolymerized units derived from TFE, at least oneethylenically-unsaturated monomer of the formula CF2═CF—O—Rf′, and atleast one ethylenically-unsaturated monomer of the formula CF2═CF—Rf. 4.The composition of claim 3 wherein the thermoplastic fluoropolymer hasinterpolymerized units derived from 85-98 wt % TFE, from 15 to 2 wt % ofa monomer or the formula CF2═CF—O—Rf′, and up to about 6 wt % of amonomer of the formula CF2═CF—Rf.
 5. The composition of claim 1 whereinthe thermoplastic fluoropolymer has interpolymerized units derived from60 to 80 wt % TFE, about 10 to about 25 wt % of a monomer of the formulaCH2═CR2, up to about 15 wt % of a monomer of the formula CF2═CF—O—Rf′,and, optionally, up to about 30 wt % of a monomer of the formulaCF2═CF—Rf.
 6. The composition of claim 5 wherein the thermoplasticfluoropolymer has interpolymerized units derived from 60 to 80 wt % TFE,about 10 to about 25 wt % of a monomer of the formula CH2═CR2, and about10 to about 25 wt % of a monomer of the formula CF2═CF—Rf.
 7. Thecomposition of claim 1 wherein th thermoplastic fluoropolymer hasinterpolymerized units derived from TFE, HFP, PPVE, and olefin selectedfrom ethylene and propylene.
 8. The composition of claim 1 wherein thethermoplastic fluoropolymer has interpolymerized units derived from TFE,at least one ethylenically-unsaturated monomer of the formula CH2═CR2,and at least one ethylenically-unsaturated monomer of the formulaCF2═CF—O—Rf′.
 9. The composition of claim 1 wherein the thermoplasticfluoropolymer has interpolymerized units derived from TFE, at least onethylenically-unsaturated monomer of the formula CH2═CR2, at least oneethylenically-unsaturated monomer of the formula CF2═CF—Rf, and at leastone ethylenically-unsaturated monomer of the formula CF2═CF O—Rf′. 10.The composition of claim 1 containing greater than 1 to about 10 wt %hydrocarbon polymer.
 11. The composition of claim 1 containing from 1 to5 wt % hydrocarbon polymer.
 12. The composition of claim 1 containingfrom about 4 to about 11 wt % conductive filler.
 13. The composition ofclaim 1 wherein the conductive filler is selected from carbon black andgraphite.
 14. The composition of claim 1 having a melt flow indexgreater than about 1 gram per 10 minutes.
 15. The composition of claim 1having a volume resistivity below about 100 ohm cm.
 16. A shaped articlecomprising the composition of claim
 1. 17. A melt-processable conductivefluorothermoplastic composition consisting essentially of: A) a majoramount of at least one melt-processable, thermoplastic fluoropolymerhaving its interpolymerized units derived from (i) at least 50 wt % ofTFE, and (ii) one or more ethylenically-unsaturated monomers representedby the formula (a) CF2═CF—O—Rf′, and, optionally, one or moreethylenically-unsaturated monomers represented by the formula (b)CH2═CR2 wherein Rf′ is a perfluoroalkyl of 1 to 8 carbon atoms or aperfluoroalkoxy of 1 to 8 carbon atoms, and R is selected from H, F, Cl,or an aliphatic group having from 1 to 8 carbon atoms which may have For Cl substituents, provided that the thermoplastic fluoropolymer hasless than 5 wt % of its interpolymerized units derived from VDF; B) fromabout 0.1 to about 10 weight percent of a hydrocarbon polymer; and C)from about 1 to about 20 weight percent of conductive filler.
 18. Amethod of making a melt-processable conductive fluorothermoplasticcomposition comprising the steps of; A) providing a major amount of atleast one melt-processable, thermoplastic fluoropolymer having itsinterpolymerized units derived from (i) at least 50 weight percent (wt%) of TFE, and (ii) one or more ethylenically-unsaturated monomersrepresent by the formula (a) CF2═CF—O—Rf′, and, optionally, one or moreethylenically-unsaturated monomers represented by the formulas (b)CF2═CF—Rf, and (c) CH2↑CR2 wherein Rf is a perfluoroalkyl of 1 to 8carbon atoms, Rf′ is Rf or a perfluoroalkoxy of 1 to 8 carbon atoms, andR is selected from H, F, Cl, or an aliphatic group having 1 to 8 carbonatoms which may have F or Cl substituents, provided that thethermoplastic fluoropolymer has leass than 5 wt % of itsinterpolymerized units derived from VDF; B) providing from about 0.1 toabout 10 weight percent of hydrocarbon polymer; C) providing from about1 to about 20 weight percent of conductive filler; D) mixing thematerials of steps A through C in any order; and optionally E) meltprocessing the mixture.
 19. The method of claim 18 wherein the materialsof steps A and B are premixed before step C.
 20. A method of improvingvolume resistivity of a melt-processable conductive fluorothermoplasticcomposition comprising the steps of claim
 18. 21. A method of improvingmelt processability of a melt-processable conductive fluorothermoplasticcomposition comprising the steps of claim 18.